Megaliths. Sacsayhuaman, Cusco, Peru

The image show the stones (megaliths) that make the ruins of Sacsayhuaman in Cusco, Peru. The size of the stones, together with their interlocking patterns make this an authentic mystery. Who built this complex? How long ago? Mainstream historians and archeologists say that they were built by the Incas in the 14th century C.E.
What do you think?